Help with mold making for Silicone puppet!

I am in the process of making a 12 inch tall 1:6 scale silicone puppet, and have reached a point where I have several questions, so forgive the length of this post.

To start, here are a couple of pictures of my armature and the sculpt:

After several months and a couple of wasted attempts at mold making, I am about to begin work on what I hope is the final mold for my character. It will be made from ultracal30. Ron Cole has a great mold making video, but at the beginning he mentions its for a foam latex puppet, but i imagine the same method can be used to make a silicone puppet.. are there any modifications that would need to be made? Im debating between the horizontal cast seen in the link just below, and the vertical cast as seen in Ron Cole Mold-Making tutorials on youtube. I have been taking bits and pieces from several mold making videos, especially Ron's and this one...

Whats the best way to mold/cast my puppet, especially with regard to floating the armature in the mold cavity?

Because my character will be wearing a short sleeved shirt, I would like to cast the entire puppet as one piece to avoid seams... arms, head and all... but it seems there is not good way to suspend the armature in the cavity when the arms (and possibly head) are attached to the armature.

It looks like Laika casts horizontally, and suspends their armatures by having their arms and legs removed and locking the body in place with miniature blocks and rods that fit perfectly inside the mold (See picture below). Is this considered the ideal way to cast silicone?

It seems the issue of hiding seams of attaching the arms to the body is nonexistent for Laika's puppet, because he will be wearing long sleeves. But how would you attach separately cast arms (or a head) to a puppet without hiding behind long sleeves. Will silpoxy, the silicone adhesive from smooth-on, allow me to simply glue the pieces to each other and then hide the seam with silicone?

I am also considering removing the head and casting everything vertically in a two piece vertical mold as shown in this picture of a puppet made by Nick Hilligoss.

It seems this vertical "Pour through the neck hole" would be the easiest way to float the armature inside... Does the shape of my puppet present any problems with air bubbles collecting in any areas?

I have watched Ron Cole's mold making tutorials on youtube, but am wondering if the same method can be used to cast a silicone puppet, and if so will i hate my life for trying to cast the puppet with the armature's hands attached? Would i need to paint the inside of each piece with silicone to give a a skin before i pour in the remaining silicone?

One final question! I have heard many people praise platsil gel 10, but it has a 6 minute pot life... too short to degass and pour i imagine... Is degassing necessary with platsil gel 10? It seems i would need a longer curing silicone to degass and eliminate air bubbles, perhaps a tin silicone. any suggestions on casting material? I have messed with soma foama and its 30 second pot life makes it unusable for me, i am leaning toward plastigel 10 but am open to other suggestions

Ultimately, my questions are these...

What is the best way to create a mold for my puppet that will allow for floating the armature inside? Could me puppet be cast as one piece? If not, how does one go about hiding the seams created by attaching a separately cast arm (without resorting to long sleeves). and finally... is degassing ideal when using platsil gel 10? Any other flexible silicones with longer pot life to allow for degassing?

Replies to This Discussion

Looking at your sculpt, I don't see anywhere air would get trapped in the body if you did decide to cast it standing up. Your arms, and all the fingers, point down so the air would rise out of them ok. The only place to look out for is in the head. The tops of the ears are the most likely spot. I think, with the slope on the bridge of the nose, there wouldn't be an air trap there.

I don't worry about de-gassing with silicone puppets, because I always paint a skin on first. Usually 3 thin layers, since the silicone tends to keep flowing slowly for a long time, and will run off the sides and collect in pools at the bottom if you try to paint on too much. The brushing takes out any bubbles. If there are some small bubbles in the stuff poured inside, at least it is not on the surface, so as long as they are small they aren't a problem. When I worked making silicone moulds for plaster architectural ornaments (in 1980s), the silicone was all poured with no skin painted on, so we always degassed it. But it had a pot life of several hours, and took 3 days to cure.

The skin also means the armature can't end up right on the surface, but it can get closer than you want. So I also put a thin layer of foam on the armature. The foam bandage underwrap, only about 1mm thick, is good for hands. (Looks like this, but it's called "adhesive", then described as non-adhesive, which it should be, so I'm not sure. https://www.optomo.com.au/product/sideline-adhesive-sports-foam-75/... Look on Amazon. ) I spray glue the foam onto the finger wires. That keeps the wire a little bit away from the outside, and gives something for the silicone to sink into and get a good grip. Bare finger wires do have a tendancy to poke through the skin after a while. I used to get 3mm thick foam sheet, can't find it now and have to use 6mm and trim it back - that keeps the limbs and chest block more in the centre. I did put in a block of foam in the belly area with that Sumo wrestler, but that was a mistake - the silicone soaked right in and the foam made it stiffer and hard to bend at the waist. But I don't see a big problem with your character, who isn't so fat.

I used Platsil Gel-10 for painting the skin, but a softer silicone - Smooth-On Ecoflex 00-30 - for filling it, because it is softer, and also thinner and pours better. But the runniness was not so good for painting the skin on, it needs more coats, and since I had some Platsil left I used it.

The pot life is fine for painting skin, quick is good. And you don't need all that long to pour, either. But with some Platsil that was getting too old, it started to thicken and go stringy really quickly, so there was a problem with it blocking the neck hole with a bubble of air under it.

For heads, I worked out a removable neck block system, that would hold the head armature in exactly the right spot. First I painted on a couple of coats of skin all over. Then I part filled the face, and placed the armature in, so the level of silicone covered some of it, and when set it would hold the head armature in place. It was also held by the neck wire going into a wooden block. Then I removed that block, put the two halves together, and poured in the rest of the silicone. The armature was held in place by the silicone in the face that had already set, and the block was removed so I could pour through the neck. (See it here, if you haven't already: https://www.youtube.com/watch?v=5fWdZnQRzB0 )

I think the horizontal casting method for the whole body would work for getting enough silicone in to hold the armature in place, as I do with the head. Their seam line is flat, so it would fill to the halfway mark all over. I would do the front first, so the jaw wires and eyeballs fit into place. Maybe once that sets, with the armature in it, you fill the back half, and put the front on top of it, and the excess squishes out? My dividing line is not flat, it goes up and down with the bend of the knees and angle of the body, so I wouldn't get as much into either half. I'd end up with some unfilled spaces for sure.

If you wanted to fill it vertically, with the head on, if there was going to be a wig added, you could have a hole in the top of the head to pour through. Then you'd hide it with the hairpiece. If you painted plenty onto the ears, there might not be much of an air bubble in there.

If you have short sleeves, you can make the entire arm as a separate piece, and attach it. If there are no sleeves, like singlets or no shirt at all, best to make the arm and hand as part of the body.

One more thing - you could have a small bleeder hole in the tops of the ears to let the air out. When the silicone rises and starts to come out, slap a wodge of clay over it. That's what we did with the high points in the moulds at the plaster factory.

The vertical Ron Cole method of creating a mould is fine, but it has one big disadvantage - gravity works against you. The best thing about laying the figure down flat is that you can pour or spoon your plaster into place. Better still is that agitating the mould a little (take care not to dislodge anything) encourages air bubbles away from the surface. Don't forget to lightly brush the plaster over the sculpt first to ensure it gets into all the crevices.

I have found that Platsil gel 00 and to a lesser extent 10 are a bit thick for me to get them down a narrow leg - fine if like in your illustration the hole is big and wide, but it is friction, weight and viscosity that determine whether it will slide down well. That and having another hole for air to escape.

I prefer to overfill the mould, and the best sort of mould for this is one that has a mating surface around the sculpt of around 10mm, then a gap between the two halves into which the excess can overflow. I add this after the first half of the plaster mould has been cast, although I must admit I sometimes forget. The other advantage of having a smaller mating surface area for the mould is that you get more pressure and therefore better seams. After the mould is filled I then clamp it together and stand it upside down, I.e. feet uppermost, when I can pour a little in if necessary or time allows.

I should add that when making the mould I have attached the feet to some clear perspex, which I then screw to my baseboard before making the clay surround. My walls are made of plastic damp proof material, available on a roll from builder's merchants, held in place with water clay. I'll try and post a picture of this.

(Not sure how to continue text underneath the pics, so entering as separate replies.)

Next pictures show the finished sculpt with perspex piece attached to the feet and screwed to the baseboard, then with the soft clay (I use Chavant NSP hard for the sculpts and soft for the surrounds) built up around the figure to the seam line, with keys in the clay. This also shows my walls, which are damp proof material (thick black plastic), taped to the perspex and otherwise held in place with lots of water clay. I'm saving up for enough Lego bricks!

Then the Crystacal (dental stone) plaster is put into the mould. I don't tend to use any release agent at this stage, as I worry that Vaseline may just ruin the detailing. The only bits that have a little Vaseline are the exposed brass tubes. I always mix plaster into water, remembering that the ratio is about 1 water:3 plaster, so filling my mixing container only about 1/4 full, and mixing enough in one go for most of the mould half. I lightly brush and blow the first plaster into the details of the sculpt, trying to release any trapped air.

Then I pour more plaster in, onto an area that is away from the sculpt itself. It should now cover the sculpt. At this point I add some glass fibre mat or burlap, taking care not to press it down into the plaster too much, as I do not want it to go right through to the mould surface. Also good is not to knock the sculpt with a fingernail or tool!

Once the plaster has fully set (gone hot then cold again), I remove the walls and turn it upside down. I remove the soft clay that formed the bed surrounding the sculpt and check very carefully around the edges of the sculpt itself to make sure that there are no lingering bits of soft clay or bits of plaster. I also repair any damage to the sculpt that might have occurred in building up the bed. And I add overflow channels and slots for me to get a screwdriver in. You can see these as lighter grey in the first pic.

Then I build the walls up again. Once again I tape the DPM to the perspex (which has remained in place throughout), then add the water clay surround. But this time the water clay has to come much higher as it has to stop the plastic from falling away under the weight of the plaster. (Once again, I must get that Lego!)

I add little bits of soft Chavant all round the edges, making sure that it creates a seal between the wall and the plaster. I check that the plaster cannot flow out or round anything. Then I brush a couple of coats of Vaseline thinned with white spirit onto the exposed plaster and the brass. I make sure that the edges up against the sculpt are thoroughly coated and there are no missed spots. (Usually these remain bright white so are easily seen). Then I do the plaster just like the first half.

Once the plaster has set, I take off all the walls and the perspex base and put a couple of screwdrivers into the slots, gently prising the mould open a little. I then take it carefully apart. The soft clay comes off easily, but the hard sculpt clay, with the armature inside, needs a bit more gentle persuasion, so I put it into the oven to warm it a little (oven should be at just over 100 deg C) Once the clay has softened a little, I can remove it very gently and pull out the armature. Often it comes away cleanly, but there may be some tiny bits of clay that need a blunt tool (or will come off with the first silicone cast!)

I put both halves of the mould into the oven for a couple of hours to dry them, and then check that the fit together properly. At this stage I check that the armature can fit in the mould and not prevent it from closing. My latest armature needed a bit of the epoxy putty shaving off and the chest reducing to get it to fit with some space around it. You can see the lighter places where I went right down to the armature in the sculpting, so needed to trim the putty back.

So there it is, almost ready to go. I just need to make up a second armature for the next time I use the mould and cover this one with the sports wrap foam. Then it's into the silicone process, as Nick described. I only finished this mould this morning, so I'm not there yet, but I hope sharing my method with you has helped.

Here's the filled mould in the vice. BTW it took about 100g of silicone to do the final fill of this mould, quite a bit overflowed, but there were no air bubbles at all in the resulting piece. The feet were filled last, once the mould was upright. This was a bit fiddly, but I am not too worried about the feet on this character as he will have shoes and/or bits of cloth on his feet. Sorry no pics of filling the mould - messy, and I have only 2 hands!

This is the final figure - with head and hands that don't match colour wise! Very pleased with how it has come out. Now for the next...!

Just a final note on the arms. The brass tube join is below the elbow, and I didn't give much thought to creating a neat join, as there will be clothing over it, well, rags, but enough to disguise the join.

Wow, thank you Nick and Simon for your incredibly detailed and helpful responses!

I am going to do some R and D and try both methods, horizontal and vertical mold making.

First I am going to attempt to cast vertically, through a hole in the head which will be covered by a hat. The puppet will be cast in one entire piece using Ecoflex 00 30 as a filler, and platsil gel 10 as a skin. Here are a couple more questions if you don't mind:

Nick,

When you paint your 3 skins of platsil gel 10 on, how do you deal with the seam and the color difference that i imagine there would be between the Platsil gel skin, and the Ecoflex filling showing at the seam? Do you pay special attention to making sure you paint all the way up to the very, very edge of the mold cavity's rim to prevent the line of ecoflex that would show otherwise? How do you maintain color continuity between different batches of silicone. Do you eyeball the matching of color between the gel 10 and ecoflex?

Simon,

you mentioned that having an escape hole for air is important in allowing the silicone to slip into all areas of the mold. If I am casting vertically, and have only one hole on top for pouring...should i incorporate a vent hole? The silicone will be poured through the head, would it be a good idea to place a vent hole in his back, then plug it with clay as the silicone reaches the level of the hole as it is poured? I also plan to plug the two small holes at the bottom in the feet region caused by the armature inside the clay figure. Also, your armature looks like it leaves little room for the silicone to slip by. Did you have any issues with pouring? I was worried about my puppet's neck bottle-necking the silicone, but your cast looks successful and gives me hope in pouring silicone down such a small space. Thanks for your help, and next week when do a horizontal mold i would love some more advice.

Here's my plan:

Cast puppet as one piece verticaly. Pour spout in head hidden by hat. Overfill channels along puppet. Vent shaft angled up and out of mold just underneath neck at the top of the back. Skin the mold with plastil gel 10, and fill wil ecoflex 0030 through head. Any more thoughts?

Colour difference: I pre-mix my flesh pigment with Part B so I have plenty all the same. I just mix some of that tinted B with some Part A when I am ready to make a batch. So all the Platsil skin will be the same colour. I do the same with the Ecoflex for filling the inside, and it might be slightly different to the colour of the Platsil I used for skinning, since I do judge it by eye, but not enough to show. Yes, I paint right up to the edges of the mould, though it does tend to get thin there as the silicone flows down.

Looking at the last photo with the head in profile, make sure you get silicone into the lower lip area as well as the ears while working horizontally, that looks like another spot where rising air could get trapped if it wasn't filled before pouring vertically.

I think doing it with the head on will avoid any ugly joins at the neck, so as long as there is room around the skull for the silicone to flow down, it should be a good way to go.

It's important not to confuse the making of the mould with the filling of it. When I said Ron Cole's method had disadvantages, I was referring to the making of the plaster mould. Just to be sure we're talking about the same thing.

Ok, now the filling. What I did was to have both halves of the mould flat on the bench. First I did a thin surface coat of silicone, covering the mould and the armature. Then, after the first mix had set, I spooned the silicone into the mould halves, so it nearly filled them, but leaving out the feet as the silicone would just dribble down there. Then I placed the armature into the mould and topped up if needed.

After that I quickly placed the back (without armature) into position on top of the front - that's why mould keys are important, cos they locate it perfectly and instantly. I immediately put the mould into an upright position, so any air bubbles would go to the feet. Yours would be head uppermost. The whole mould was held together in a vice, but strong tape or some clamps would also be fine. The vice acts to hold the mould in position. Finally I dribbled silicone into the feet to ensure they were filled.

I would recommend that you use some retarder in your mix, to give time for the silicone to flow and bubbles to escape. I would also recommend you fill as much as you can before closing up the mould. You are right that the silicone would not get round my armature easily, but not would it travel down your mould before it set. Ideally you want to have enough silicone in the mould so you are just topping it up with the pour. Don't add a hole in the back. I think this is unnecessary and will prevent you from filling the mould half horizontally. The head hole should be sufficient, but remember that when pouring, you should dribble the silicone down one side, to allow the air to escape.

I mix up one batch of colour and use that for all mixes, but care has to be taken not to over-colour the small batch and under- colour the main, as I just foolishly did on another piece.

Just to summarize: I don't think your plan will work. You are right that the neck, and other bits of the armature will bottleneck the silicone. Fill flat, add armature, slap it together, hold upright and fill head!

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